Harry Harrison would like to have a word with you.
Back on the topic, there was a one season show with this premise (mostly, anyways).
So would Bill Watterson.
I don’t remember there being any time travel in that film. You see multiple realities happening at the same time, but there’s no going back or forward in time.
And I just remembered another one. It’s not time travel per se, but communications between past and future are used to affect the future in positive ways.
Similar to Frequency, there’s The Caller.
Happy Accidents. A pleasant little romance in which one of the lovers has convinced himself that he’s a time traveler. It’s much better than it sounds.
Last episode of Voyager…Admiral Janeway goes back in time and not only changes things for the 'better"
But genocides the Borg as well. (Picard spoilers)
Man, Voyager sure liked time travelling to make the timeline what they wanted it to be.
BITD, on the Usenet C Adams group, it was often argued that by making a new timeline, Janeway killed every person in the universe in the old one. A view I dont hold.
I just remembered one - The Return of William Proxmire, Larry Niven’s ode to Robert A. Heinlein.
Title character goes back in time to give Heinlein antibiotics so that he stays in the Navy; scientist who built time machine to send him back decides he likes the new timeline better.
That made me think of another Japanese movie, Returner.
Milly is a time traveler from the future, where humanity is on the brink of extinction because of a war with a race of highly-evolved aliens. She jumps back to the present to try to prevent the war, and enlists the aid of daredevil shootist Miyamoto, who would really rather hang up his guns … until he finds out that his arch-nemesis might be responsible for starting the war with the aliens in the first place!
There’s a little piece at the end where Milly (she’s the “returner” of the title, not Miyamoto) gets to do something small, buy ultimately very nice for Miyamoto.
Kudo’s to you @psiekier - I actually own that DVD, and while I don’t consider it high art, I always enjoy it. I didn’t know anyone else who was familiar with it.
Of course the very best Japanese time-travel movie is Summer Time Machine Blues.